1. Field of the Invention
The present invention relates to an apparatus and method for controlling starting of an engine.
2. Description of the Related Art
In a cold start of the engine, meaning that the engine and other components are not still warm from previous use, a catalyst is in an inactive state since its temperature is low and is incapable of purifying an exhaust gas. In this situation, it is important to activate the catalyst in order for the catalyst to begin to purify the exhaust gas.
Japanese Patent Application Laid-Open (JP-A) No. 8-232645 discloses a technique for activating the catalyst after the engine is started. In the technique, in the cold start situation, an ignition timing is set at a start ignition timing until the engine is started by cranking and the engine fires. After the engine fires, the ignition timing is quickly retarded to a predetermined ignition timing after the compression top dead point, whereby the temperature of an exhaust gas is raised to quickly activate the catalyst. Further, an idling control valve is opened wide before the ignition timing retardation to thereby increase the amount of intake air, and after the ignition timing retardation, the amount of the intake air is further increased to smoothly and quickly fire the engine.
The technique of JP-A-8-232645 causes the engine to smoothly and quickly fire, but the engine rotation speed exceeds a target idling rotation speed. This reduces the fuel economy because more fuel is consumed at the higher engine rotation speed.